1. Field of the Invention
The present invention relates to low-molecular-weight and polymeric liquid-crystalline 2-substituted benzotriazoles, to the use thereof as photoconductors (compounds which transport charge carriers) in electrophotographic recording materials, and to the use thereof for fluorescent displays on the basis of the strong fluorescence of these liquid crystals.
Photoconductors are widely employed in industry in copiers, laser printers and offset printing plates.
2. Description of the Prior Art
EP-A 93 329 and EP-A 93 330 disclose electrophotographic recording materials which contain, as photoconductor, triazoles of the formula ##STR2## where R.sup.1 and R.sup.2 are, inter alia, oxygen, alkyl, allyl, benzyl or substituted or unsubstituted phenyl, R.sup.3 is hydrogen, alkyl, alkoxy or halogen and R.sup.4 is hydrogen, alkyl, alkoxy, vinyl, allyl, dialkylamino, nitro, cyano or acryloyl.
A disadvantage of the benzotriazoles used hitherto is their great tendency towards crystallization in most binder systems. Photoconductor layers are therefore frequently produced using complex mixtures of photoconductors.
A general disadvantage of organic photoconductors is their low charge carrier mobility. For use in fast laser printers or copiers, it has therefore hitherto been necessary to fall back on inorganic photoconductors, which contain toxic selenium.
On the other hand, it is known that highly ordered systems, such as monocrystalline anthracene, have higher charge carrier mobilities. There has therefore been no lack of attempts to utilize the liquid-crystalline order in low-molecular-weight or polymeric liquid crystals to produce faster photoconductors. Evidence has recently been found of increased photoconduction in the diskotic phase (cf. DE-A 41 26 496) and the nematic phase (cf. DE-A-42 11 087).
It is an object of the present invention to provide benzotriazoles having liquid-crystalline properties, in particular those which are photoconductive and have higher photoconductivity in the liquid-crystalline phase and in the non-liquid-crystalline phase. In addition, it is of interest whether the strong fluorescence of 2-aminophenylbenzotriazoles is also retained in the liquid-crystalline representatives.